Acestrorhyncinae might not be
a monophyletic group as previously believed, Menezes (1983) compared the genus Oligosarcus (Günther, 1864) and their
relationship with Acestrorhychus. Genus Acestrorhynchus are a
homogenous tribe. Most of the species can be delineated by several external
features, including snout length, coloration and maximum size. All the forms are
ichthyophagous and require good, clean oxygenated water with a warm temperate
between 23 - 28 C. I was fortunate to make some rare footage of A.
falcatus breeding behavior several years ago. A copy of the raw footage was
sent to Oregon State University in 1994.

On the left are stills of the
event. The species spent quite a few hours doing this type of
"dance".

IN THE AQUARIUM

As
hobbyists, aquarists should know that they are jumpers and need a tight fitting
lid. Also, they prefer open habitat as opposed to a well decorated tank. They're
not aggressive, and they don't appreciate aggressive fish, however they eat fish
up to 2/3rds their size. They also need a great deal of space (a tank at least 5
feet long) because they can and do kill themselves by running into the sides of
aquaria.

98-115 scales in the lateral
line; 27-34 scale rows from lateral line to origin of dorsal fin, 15-18 from
lateral line to origin of anal fin.

Acestrorhynchus briskii (Menezes,
1969)

A distinct black band on
sides of body, from upper end of opercle to caudal base; anal fin rays v, 23-27;
92-103 scales is the lateral line; 18 scale rows from lateral line to origin of
dorsal fin, 12 from lateral line to origin of anal fin.

Acestrorhynchus falcatus
(Bloch, 1794) A. falcatus is commonly found in the aquarium trade and sometimes
easily identified at young ages, by its two black spots (one behind opercle and
the other at the caudal peduncle base), and bright red fins. The species is
distributed in South America; Guyana, Amazon and Orinoco basins. The fish is
known to grow at least 20 cm and is an efficient predator similar to temperate
north American pike. It is very abundant but is primarily found in open waters
with a moderate flow. Reproduction begins at the onset of the rainy season. It
is considered harmless to humans. In the aquarium, the species does well in
small school and might be sexually dimorphic (?). With the small samples
obtained for OPEFE, the fish appears to scatters eggs and provides no parental
care.

The documented pre-spawning
behavior (furnished to Oregon State University, Neo-tropical Division)
illustrates a male fish that approaches the female and swims a type of figure 8
pattern, up and around the female, while she holds immobile. This act is
repeated several times. One can see the anal fins touch, but no evidence of
sperm being released.

Due to mortality, no further
examinations were conducted. In another situation; the egg scattering was
observed at a pet store by a dealer who had kept two specimen's in captivity.
While this information is vague, the fish provided no care to the released eggs.
Both fish were approximately 12 cm SL. No larvae emerged from the spawn released
(zygotes).

Distribution: Amazon and
Orinoco River basins and rivers of north South America: Brazil, French Guiana,
Guyana, Peru, Suriname and Venezuela.

Acestrorhynchus
falcirostris (Cuvier, 1819) Opercle with dark patches, the upper separated
from the lower by a very narrow pale stripe; 140-175 scales in the lateral line.

Acestrorhynchus
grandoculis sp. n. (Menezes & Géry, 1983) 74-85 scales in the lateral
line; 10-11 scale rows from the lateral line to origin of anal fin; eye very
large, the orbital diameter about 31.0%-38.5% of head length. The species has
very small, sometimes indistinct but strange dark blotch at the beginning of the
lateral line behind the opercle. This marking helps distinguish it from A.
microlepis (Schomburgk) and A. guianensis (Menezes) from the other
remaining species of Acestrorhynchus. Fairly common species.

Acestrorhynchus
heterolepis (Cope, 1878) Lateral line scales with two divergent branches of
the laterosensory canal (Cope, 1878). Lateral line scales with only one branch
of the laterosensory canal which is inclined either upward or downward. General
color pattern consisting of one mildlateral dark stripe running from tip of
snout to caudal base and another dark stripe extending from about end of
maxillary to lower surface of caudal peduncle, inconspicuous anteriorly and
wider above anal-fin base. A. heterolepis can be difficult to identify by
morphology or even color. They have longitudinal stripes as juveniles and
closely resemble isalinae. A helpful characteristic is the base of the tail
where there is a red spot dorsally and a yellow spot ventrally. These spots and
the stripes disappear as the fish exceeds 10 cm. At this point A. heterolepis
develops the false nose and is thus very easy to confuse with A. falcirostris!
These fish were trained to eat prepared as opposed to live food. (Tom Lorenz,
2007).

A. heterolepis -
FEEDING SEQUENCE BY TOM LORENZ

Acestrorhynchus isalineae
(Menezes & Géry, 1983) The body coloration pattern is similar to A.
nasutus (Eigenmann). Two longitudal dark stripes run across the body
(anterior/posterior). The superior stripe runs from the tip of the snout to the
caudal base. The inferior one runs from the about the end of the maxillary to
the lower part of the caudal peduncle, being rather diffuse
anteriorly. This peculiar color pattern is not found in any of the
previously known species of the genus Acestrorhynchus. The difference
with this species and A. nasutus is that it has more scales on the
lateral line (89-92 vs. 78-82), and more scales above (14-15 vs. 13-14) and
below (9-10 vs. 8-9) the lateral line. It also has fewer anal-fin rays, more
pectoral fin rays, more maxillary teeth, more teeth on the posterior part of the
dentary. The head and the snout shorter, the body longer, eye smaller and the
interorbital narrower.

Like A. nasutus it is
a small species. Sexual dimorphism is seen on the males; the midlateral
dark stripe is wider and more intense than in the female. The inferior stripe in
the male is also more prominent and dark than the female. It is most unusual to
see this type of color pattern-dimorphism in acestrorhynchin fishes. The
species type-locality may be more broader than the samples examined so far. It
may occur in other tributaries of the Rio Marmelos and the Madeira.

The species is named after
Mrs. Isaline Drecq, wife of Mr. Guy van den Bossche, participant in the
expedition which found the species. 84-92 scales in lateral line.

Acestrorhynchus lacustris
(Lütken 1875) 89-102 scales in the lateral line; 23-26 scale rows from lateral
line to origin of anal fin, 13-16 from lateral line to origin of anal fin.

Acestrorhynchus
maculipinna sp. n. (Menezes & Géry, 1983) This species has the same two
longitudinal dark stripes on the body that characterizes the color pattern of
both A. nasutus and A. isalinae and set these 3 species apart from
the remaining species of the genus. It differs from the other two species and
all others by its very prominent large black spot on the dorsal fin.

Acestrorhynchus microlepis
(Schomburgk, 1841) Considerable variation exists within specimens identified as A.
falcatus and A. microlepis. Based on morphological and coloration
differences associated with geographic distributions, we identified an
undescribed form of A. falcatus from Casiquiare drainages (southern
Venezuela), and another from the middle-lower Orinoco Basin. The extensive
morphological, meristic, and coloration variation observed in A. microlepis
does not appear to be associated with geographic distribution, but further
analysis is needed. Based solely on juvenile specimens. (H.
Lopez-Fernandez and K. O. Winemiller, Wildlife and Fisheries Sciences 2000 -
2001 Annual Report).108-122 scales in the lateral line; 20-22 scale rows from
the lateral line to origin of dorsal fin, 15-18 from the lateral line to origin
of anal fin. Syn. A. cachorro.

A. apurensis (Toledo-Piza
& Menezes 1996) was described as an endemic within Venezuela’s western
llanos Synonym of Acestrorhynchus microlepis (Schomburgk, 1841): Acestrorhynchus
apurensis (Toledo-Piza & Menezes, 1996). Diagnostic characters of A.
apurensis grade into certain morphotypes of A. microlepis. It was
concluded that A. apurensis is either a valid species with a broader
distribution than previously believed, or is an invalid name based description
of juvenile A. microlepis, a highly variable species.

Acestrorhynchus minimus
(Menézes, 1969) Black band absent on sides of body; a rather dark stripe from
upper end of opercle to caudal base; anal fin rays v, 21-25; 74-86 scales in the
lateral line; 12-14 scale rows from lateral line to origin of dorsal fin, 8-10
from lateral line to origin of anal fin.

Acestorhynchus nasutus
(Eigenmann, 1912) (See A. isalineae above) General color pattern consisting of
one midlateral dark stripe running from tip of snout to caudal base and another
dark stripe extending from about end of maxillary to lower
surface of caudal peduncle, inconspicuous anteriorly and wider above anal-fin
base. No distinct black spot on anterior basal part of dorsal fin. Considered
rare. 78-82 scales in the lateral line.

I take this
opportunity to thank Naercio Menezes for making his citations available in
order to construct this web page. While most of the material is technical in
nature, it still is helpful to those of you who are interested in the fish at a
systematic level than just an aquarium pet. The key provided here are accurate
to the citation and some notes mentioned are my own and not necessarily those of
the author N. Menezes.

Toledo-Piza, M. and
Menezes, N. A. 1996. Taxonomic redefinition of the species of
*Acestrorhynchus* of the *microlepis* group with the description of
*Acestrorhynchus apurensis*, a new species from Venezuela (Ostariophysi:
Characiformes: Characidae). Am. Mus. Novit. 1-23.

The OPEFE web
site and its contents; is disclaimed for purposes of Zoological Nomenclature in
accordance with the International Code of Zoological Nomenclature, Fourth
Edition, Article 8.3 and 8.4. No new names or nomenclature changes are available
from statements at this web site.